Controlled fiberization is a process for the application onto substrates of coating materials, such as pressure sensitive adhesives. The process was developed from air-assisted and melt-blown technologies. It provides a method of applying a continuous fiber of adhesive on a substrate surface in a dense distribution of precise width, fine edge definition, and specific fiber thickness, and achieving a controlled uniform density of the adhesive material on the product.
With controlled fiberization, a high viscosity material such as adhesive is dispensed in a continuous flowable stream or fiber, usually in the form of a swirling three dimensional spiral pattern extending from a dispensing nozzle onto a substrate. The swirling movement of the pattern is a result of the ejection of the high viscosity material under pressure from a nozzle to form a continuous adhesive fiber, then directing streams of air onto the fiber from a circular array of skewed air jets spaced around the nozzle to propel and swirl the material into a rotating pattern which moves toward the substrate. The air streams, together with the forward momentum and centrifugal force of the ejected material, force the material into a rotating outwardly spiraling helical pattern in which its own cohesive and elastic properties hold it in a string-like or rope-like strand.
Controlled fiberization methods for the application of pressure sensitive adhesives and the devices using such methods are described, for example, in U.S. Pat. No. 4,785,996 entitled ADHESIVE SPRAY GUN AND NOZZLE ATTACHMENT assigned to Nordson Corporation, Amherst, Ohio, the assignee of the present invention, and hereby expressly incorporated herein by reference.
The use of controlled fiberization techniques requires, for the above described advantages to be realized and the industry demands to be met, proper control of the application process and proper functioning of the dispensing apparatus. Absent accurate control of the system parameters and proper function of the dispensing device, some or all the above advantages are lost, including particularly those affecting the quality of the products and the cost and efficiency of the dispensing operation.
Accordingly, there is a need to provide coating material dispensing systems and processes, particularly controlled fiberization dispensing systems and processes for the application of adhesives, as for example pressure sensitive adhesives, and to provide the dispensing operation with monitoring capabilities that can accurately, quickly and economically determine the performance of the system components and of the adhesive application process.